Measures derived from the slope of the linear relationship between systolic and diastolic pressures obtained by 24-h ambulatory blood pressure (ABP) measurements incorporate clinical and prognostic information, and are believed to be vascular markers. Using post hoc analysis, we investigated potential changes of these 'slope-related measures' in three different studies conducted in hypertensive patients with before and after 24-h ABP measurements, and also evaluated the sensitivity of the results to the analysis method. Two interventional studies included 8-week device-guided breathing (DGB) exercised by 13 patients with uncontrolled blood pressure (BP), and a 6-month mineral potassium chloride-enriched diet administered to 20 elderly patients. One study was observational and involved winter-to-summer change experienced by 13 patients with controlled BP. Slope-related measures included systolic-on-diastolic slope and its equivalent 1-(diastolic-on-systolic slope) called Ambulatory Arterial Stiffness Index, and were determined using three different BP-averaging methods and two types of regression procedures. Results demonstrated sensitivity of slope-related measures to the analysis method, the most significant changes were found when the before and after 24-h ABP profiles included hourly averaged BP further averaged over the patient population, and slope-related measures were determined using symmetric (and not standard) regression. DGB was found to reduce significantly all these measures. The changes in the slope-related variables for individual patients correlated negatively with its baseline value and positively with the observed pulse pressure changes. In conclusion, the study provides evidence that DGB can affect positively vascular markers associated with cardiovascular risk, and suggests improved analysis methods for the determination of slope-related measures in interventional studies.